Power quality is critical in terms of an engineering aspect of a power system and an efficient power supply. Also, power quality is now more significant due to the competition of power market.
Along with the development of power electronic technologies, installing a nonlinear load at each customer increases. Since the increase in a nonlinear load installed in a distributed power system customer generates a harmonic distortion in a current waveform flowing in each electrical load, a current waveform distortion is caused. Such a disadvantage generates distortion power in a power transfer process, and thus a power system is inefficiently operated and low quality power is supplied to a customer.
A selection of load, which generates distortion power and causes a deterioration of power quality, is critical to prevent power quality from being deteriorated due to an increase in a nonlinear load. A power quality index with respect to each load of a customer is to be first measured for the selection of load. In this instance, a power quality index is to be measured considering the generation of distortion power.
However, a power quality index measurement in a conventional art does not consider a distortion power generation of each load. Accordingly, the power quality index measurement is not closely related to distortion power associated with actual power quality. For example, since a total harmonic distortion (THD) measurement considers only proportion of waveform distortion, distortion power associated with actual power quality is not fully reflected.
Accordingly, a development of power quality index measurement method, which may show distortion power generation caused by a harmonic generated from a nonlinear load as a quantified value, is required.